Regulating means for pressure cabins



S p -10 1946. 3 .1mm 2,407,257

REGULATING MEANS FOR PRESSURE CABINS Filed Feb. '7, 1942 2 Sheets-Sheet1 B'RucE E. 'DELMAR C(ttorneg Zhmentdr Sept. 10, 1946. B. E. DEL MARREGULATING MEANS FOR PRESSURE CABINS 2 sheets sheet 2 Filed Feb. 7, 1942I I I:

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5 1a m N /lllllral!lllltlrl Snventor Gttorncg Bauer? 5 DELMAR PatentedSept. 10, 1946 UNITED S TATES PATENT OFFICE REGULATING MEANS FORPRESSURE CABIN S Bruce E. Del Mar, Los Angeles, Calif., assignor toDouglas Aircraft Company, Inc., Santa Monica, Calif., a corporation ofDelaware Continuation of application Serial No. 285,216,

July 18, 1939.

1942, Serial No. 429,901

tion, Serial No. 285,216, filed July 18, 1939, for

Cabin pressure control, and relating to means for maintaining in thecabin of an aircraft flying at high altitude a pressure corresponding toa lower altitude so that the'comfort of the passenger will be preserved.Many persons living ordinarily at low altitudes suffer considerablediscomfort at altitudes of 12,000 feet or greater, and to all personsrapid changes of pressure cause discomfort.

Most aircraft passengers, however, can readily tolerate altitudes in therange of 5,000 to 10,000 feet, and, in view of this fact, it isstructurally and mechanically advantageous to design a pressure cabinfor a certain moderate pressure differential. It is then desirable togradually reduce the cabin pressure during ascent at a lesser apparentrate of climb than that of the aircraft, but in a manner such that thepermissible pressure differential is never exceeded. Similarly, duringdescent, the cabin pressure may be gradually raised in order to equalthe existing ambient atmospheric pressure shortly before landing.

It i the principal object of my invention to provide an improved meansfor controlling pressure within an aircraft cabin in such manner thatnot only will predetermined pressure values be maintained within therange of altitude in which the aircraft i flown, but also rapid pressurechanges within the cabin resulting from use of known pressure regulatingequipment will be avoided and actual optimum passenger comfort andsafety will be achieved.

Another object is to minimize the pressure changes to which occupantsare subjected while the aircraft climbs or descends at a high rate orencounters bumpy air.

It is an object of the invention to provide with or in air flow and/orpressure regulating mechanism of any of thetypes suitable for control ofthe flow and pressure of air in an aircraft cabin, means foranticipating pressure changes and to compensate for or check suchchanges.

An' additional object is to provide mechanism to compensate for surgesand sudden'changes in compressor air delivery and further to compensatefor sudden variations in air exhaust.

The anticipator system which forms a principal part of the presentinvention has for its purpose to provide a means for anticipatingpressure changes which will be produced in the cabin .in-

" t'erior as the result of changes in air flow through This applicationFebruary 7,

2 either the air inlet duct or the air outlet duct of the cabin. Thisanticipator system is connected to the cabin pressure controlling meansand causes the same to operate in a manner to anticipate changes incabin pressure which the changes in air flow would effect if the outletvalves of the air system were not readjusted in accordance with thedifferent relative rates of flow of air through the inlet and outletducts of the air system of the pressure cabin. By use of the presentinvention the condition known as hunting in the operation of controldevices of this general character is reduced to a minimum.

Other and further objects will become apparent as the descriptionproceeds.

For a clearer understanding of my invention, reference may be had to thedrawings in which:

Fig. 1 is a perspective schematic view of an embodiment of my cabinpressure control system, a fragmentary portion of the aircraft beingshown in phantom.

Fig. 2 is a, partially sectional and partially schematic view ofcomponents of the pressur control system including a cabin pressureregulator, and the electrical. system for controlling the cabin outletvalves.

Fig. 3 is a schematic diagram of an outlet valve limit switch system forcontrolling blower air delivery.

Fig. 4 is an explanatory view showing a twoway valve through whichpressure enters the cabin pressure regulator, this view also showing theparts of the anticipator system which are connected through the valvewith the cab-in pressure regulator.

Fig. 5 is a fragmentary partly sectioned view showing a manner in whichthe inflow of air to the cabin may be controlled.

Referring now to the drawings, an airplane 6 having wings, fuselage,control surfaces, power plant, etc., is equipped with a cabin 8 adaptedto withstand a desirable pressure differential, or, in other words, tobe supercharged. Pressure in the cabin is supplied by one or moreblowers l0 and is regulated primarily by one or more controlled cabinair outlet valves 12 which may be connected, as shown, by a cable [3 forsimultaneous operation. The blowers receive fresh air preferably from thnose of the fuselage through a ram duct system I4 and deliver compressedair to the cabin through ducts l6 or through a conventional heating andventilating system. The duct system l4 comprises three conduits, two ofwhich lead directlyto the blowers l0 and the other one of which leadsdirectly to the cabin duct system.

I) The latter conduit is the largest of the three and incorporates acheck valve I which is adapted to close the aft portion of this duct toincoming air as soon as the blowers begin operating and build up apressure in the cabin greater than the flight ram pressure. In fact, myinvention is such that there need be no difference in the distributionof fresh air or its temperature control mechanism, whether or not the.cabin is supercharged. In order to accomplish supercharging orpressurizing, however, it is necessary that the cabin, cabin air exhaustvalves, ducts and other associated parts be designed to withstand apressure difierence.

The controlled cabin air outlet valves I2, [2 are supplemented by largeroverhead'exhaust outlets l8 for discharging sufflcient vitiate'd airfrom the cabin and lavatories in unsupercharged flight. These largeoutlets are especially needed to insure ample ventilation in hotweather. While I have shown only two controlled cabin air outlet valvesl2, l2, there may be three or more in a passenger airplane, dependingupon the cabin size, and these may be interconnected by suitablemechanism so as to act partly in series, partly in parallel. A pluralityof these valves, diiierently located, is advantageous because, whenflying supercharged, it is desirable to exhaust the air mostly from thelavatories or dressing rooms which may be situated at opposite ends ofthe cabin.

When ascending, and desiring to supercharge, the large outlets i8 areclosed and the quantitative outlet control is turned over to the smallervalves 52, I2 which can be more accurately regulated and whichpreferably discharge into such unsupercharged fuselage portions asbaggage and cargo compartments, thereby not only heating these portionsbut also precluding the possibility of icing occurring in the outlets.The control of the valves l2, l2 can be operated manually as by a handle2!! in case of emergency, but normally this control is effectedautomatically by a servo system, broadly referred to as 22, which isresponsive to a cabin pressure regulator 24. In determining the efiectof changes in the setting of the valves 12 upon the pressure in thecabin, consideration may be given to the escape of air which willinevitably occur through any leaks in the wall of the cabin as, forexample, at fabricated joints. It is to be understood, therefore, thatin referring, in the ensuing specification and claims, to the control ofcabin pressure by controlling the cabin outfiow, I do not intend toindicate that the entire outflow is controlled. Obviously the loss ofair through unavoidable leaks is an uncontrolled outflow. However, theinvention does provide for controlling a sufiiciently large percentageof the outflow to exercise a fully effective control upon cabinpressure.

In general, the anticipating control mechanism functions in response toa differential in transient changes in the quantities of flow in theinlet and outlet means respectively to adjust the cabin pressureregulator so as to prevent any substantial deviation of cabin pressurefrom a prescribed maintenance value, bearing a predeterminedrelachanging in accordance with the predetermined schedule.

Although my invention may be used with various types of regulators,having rate of climb control, lag means, or a single element respondingto and limiting cabin pressure, the regulator 24 I have shown as anexample comprises a case 26 which houses a pair of coacting pressuresensitiveunits 28, 30, unit 28 being a sealed bellows, such as employedin aneroids, adapted to react to cabin pressure and unit 30 being abellows having its interior connected through a duct 54 with theexternal atmosphere so that it will expand' and contract in keeping withchanges in the difference between cabin pressure and flight altitudepressure. A pointer or lever arm 32 is pivotally connected both at 34 toa bracket 36 fixed to the housing and at 38 to the coacting units. Thelever arm is adapted to touch neither or either of two spaced contacts46, 42 dependent upon pressure reactions of the units 28, 30. A scale M,together with an index, is provided on the face of the instrument toindicate the regulator setting. Adjustment of the regulator isaccomplished by a knob 45 to which the scale is geared for rotation. Thecontacts 40, 42 are also adjustable with relation to the lever 32through the knob control.

As shown in Fig. 2, the cabin pressure unit 28 is an aneroid which isexternally exposed to cabin pressure either directly or through aconduit I36 connected to a two-way valve 48 such as is shown in Fig. 4,and the unit 32 is a pressure diaphragm exposed to the pressuredifferential between flight altitude pressure and cabin pressure, theflight altitude pressure being carried to the unit through a conduit 56which, as shown in Fig. 1, extends to the exterior of the cabin 8.

If an altitude ratio control of say 1 to 2 is desired, that is, cabinpressure controlled substantially halfway between flight altitudepressure and equalizing altitude pressure, and if the sensitivity of thetwo regulator units is alike, they can be merely superposed as shown inFig. 2. That is to say, the aneroid 28 is mounted on the upper wall ofthe bellows 30. An increase in external flight pressure, transmittedthrough the duct 54 to the interior of the bellows 30, causes the sameto expand vertically, lifting the aneroid 28 bodily and swinging theswitch lever 32 upward. Likewise, a reduction in external flightpressure will be transmitted to the interior of the bellows 30, allowingthe same tocontract so as to lower the aneroid and swing the lever 32downward. An increase in pressure within the case 26 of the device 24,which may be connected to the interior of the cabin through the pipeI30, will cause both the aneroid 28 and the bellows 3%] to contractvertically, with the result that the lever 32 will be swung downward,and a decrease in the pressure in the case 26 will result in expansionof the members 28and' 3U and a raising of the lever 32. Accordingly, theposition of the lever 32 at any time'depends'upon the relative pressuresapplied internally and externally to the aneroid 28' and the bellows 30,and when pressures in the case 26 and in the duct 54 define a proportionor ratio which is determined by the characteristics of the aneroid 28and the bellows 30, the contact lever 32 will be positioned between thecontacts 40 and 42. When cabin and flight pressure depart from thisratio, the lever 32 will be swung either upward or downward to engageeither the contact 40 or the contact 42 to energize the control circuitswhereby the required 5 opening or closing of valves I2 may beaccomplished. I

' The regulator performs three functions, one at a time; it actuates anincrease servo system when an increase in cabin pressure'is needed; orit actuates a decrease servo system when calling for a decrease of cabinpressure; or it actuates neither the increase nor decrease systems whenthe cabin pressure is substantiallythe pressure called for by thepredetermined ratio of flight equalizing altitude pressure tocabinequalizing pressure.

The regulator actuates the servo systems through theelectricalcontacts40, 42, between which the lever 32 plays, and a relay system 64,

which may include an electronic relay 65 to preclutch equipped motor 66having reversed field windings and adapted for driving suitablereduction gears in either direction to control through rotation ofshafts 66 the opening and closing of the outlet valves I2, l2 which inturn govern the area available for the flow of waste air from the cabinto the atmosphere. 'Should there be a decrease in cabin pressure or anincrease in external pressure so that the ratio characteristic of thecontrol means 28-30 is departed from, the lever 32 will be swung intoengagement with the contact 40 and the relay 64 will be actuated so asto feed current through one of the field windings of the motor 66 torotate the motor in a direction to produce a closing movement of thevalves I2, thereby decreasing the outflow of air from the cabin andincrease cabin pressure and restore the ratio. In a similar manner, anincrease in cabin pressure or a decrease in flight pressure will resultin movement of the lever 32 down into engagement with the contact 42, toactuate the relay 64 in the opposite direction and cause energization ofthe other field winding of the motor 66 and effectuate opening of thevalves I2, whereupon the increased rate of flow of air from thecabinwill causea drop in cabin pressure to restore the ratio to thepredetermined value characteristic of the members 28 and 30. At a givenblower delivery rate and at a given altitude, the cabin pressureattained will become higher as the area of the outlet valves I2 is madesmaller. The higher the flight altitude, the more the valves will haveto be closed to maintain the desired cabin pressure. When the increaseservo system is operating, the motor 66 is adapted to close the valvesand when the decrease servo system is operating, the motoris reversed toopen the valves. The speed of servo response may be varied by alteringthe speed of the motor. It may be mentioned that the servo controls maybe electric, pneumatic, or otherwise.

In my invention the positions of the outlet valves I2 cooperate incontrolling air flow into the cabin, and for this purpose a servocontrol is connected to the outlet valve mechanism so as tobe actuatedwhen the valves open or close beyond two or more set stations. As shownin Figs. 1 and 3, a motor 68 actuated by this control is provided foreach blower I to decrease or increase the flow of fresh air by more orless throttling the flow or by slowing down or speeding up the blowers.

. In Fig. 3 the outlet valve is shown as a butterflyvane I2, which, asshown in Figs. 1 and 6, is rotated by a shaft 66' adapted to be drivenby themotor '66. A portion of. this valve I2 may. servelasa movingcontact, and for, this purpose it is connected to one terminal of abattery B, Fig.3, the remaining terminal of which is con nected to themotors 68 which are shown as being of reversible series wound type. Therespective forward and reverse windings j and r of the motors 68 areconnected to contacts 0 and 0 disposed so as to be engaged by themovable contact or valve I2. When the valve I2 swings into engagementwith the contact 0, the windings f of the motors 68 will be energized,and when the valve I2 engages the contact 0 the windings 1- will beenergized. As shown in Fig. 5, each motor 68, through worm gearing 68,ashaft 68a and linkage means 68b, operates a common form of valve orgate G in the air inlet pipe I4 leading to the associated blower Ill tovary the blower air production.

As previously indicated, my invention also includes an anticipatorsystem or air pressure surge control, the objects of which are tominimize any huntingtendencies of the pressure regulating system and toincrease the rapidity of regulator response to the trends of cabinpressure variation thereby anticipating as well as materially dampingthe amplitude of air pressure variations within the cabin and preventingsurges of the cabin atmosphere. These objects can be obtained throughthe use of a conduit system I20 terminally connected at the superchargedpressure side of each blower I0 and at the cabin side of the rear outletvalve I2, and intermediately connected into the housing of the regulatorbeing utilized for primarily controlling cabin pressure. This regulator,in the operation just described, would be the pressure regulator 24. Thecabin pressure control is therefore provided with sensitivity to theduct inlet andoutlet pressures of which the cabin pressure proper is adirect function. By properly locating between the inlet and outlet endsof the conduit I20, the point of communication between said conduit andthe interior of the case 26 of the regulator 24, or by the properarrangement of the flow responsive means at the ends of the conduit I20in relation to the inlet and outlet means, it is possible to equate thepressure thus applied to the interior of the case 26 to the pressureproduced within the cabin atmosphere proper, during the normalfunctioning of the apparatus. Thus the pressure existing within the case26 may be caused to equal cabin pressure during normal operation of theapparatus and the aneroids 28 and 30 may be said to be normallyresponsive to cabin pressure. Cabin pressure, or simulated cabinpressure, is established in the case 26 during normal operation; as thefunction of the inlet and outlet pressures transmitted through theconduit I20. Pressure in the cabin atmosphere itself will of course alsobe a function of such inlet and outlet pressures,

but, because of the large volume of cabin space, there is a definitetime lag in the derivation of this function; whereas, the changes insimulated cabin pressure in the case 26 follow immediately the changesin flow conditions at the inlet and outlet, and thereby anticipate thecorresponding changes which would occur in the cabin atmos-, phereexcept for the corrective functioning of the regulator which preventsthe corresponding changes in cabin pressure under abnormal conditionssuch as transient fluctuations or sudden surges in the inlet and outletflows.

As shown in Figs. 1 and 4, the inlet connection of the anticipatorconduit I20int'o duct I6 preferably comprises a Pitot tube I22; and thecon ,75 nectlon of the conduit into duct 94ahead of the:

rear outlet valve I2 preferably comprises afVenturi tube I24 locatedwithin the outlet air flow duct 94. The purpose of this arrangement isto increase the pressure difference between cabin inlet and outlet forincreasing the flow otherwise available therein and consequentlyimproving the anticipator sensitivity. When anticipation is desired, thevalve 48 connects the conduit I30 with a branch conduit which isconnected in turn through piping I26 to the anticipator conduit I20.

As further shown in Fig. I, the venturi I24 consists of a short tube I24supported in the path of flow of air through the rear outlet duct 94 bythe end I20 of the pipe I20 which communicates with the throat I24a ofthe tube I24. Also, in Fig. 4 I have shown that the check valves I08 inthe air ducts I8 may each comprise a flap valve of well known type.

In operation, air flows through the conduit I20 in response to pressuredifferentials existing in the supercharging and ventilating system;however, any surge in pressure at the inlet or cabin outlet causes acorresponding pressure change within the conduit I26 so that thepressure reacts through the valve 48 upon the pressure sensitive unit24. Conduit I20 is, in effect, a flow system paralleling the air flowthrough the cabin proper. The greater sensitivity of the anticipationsystem then is accountable to the ratio of flow through the conduit I20,being greater in proportion to the volume of the branch conduits and theconnected regulator housing than the ratio of main cabin ventilation inproportion to the cabin volume. .Therefore, the regulating system isprovided with a sensitivity which anticipates the trend of pressurechanges in the cabin proper and it' can counteract and control any surgebefore it becomes apparent in the cabin. The theory of operation of theanticipator system is as follows. The interior space of an aircraftcabin of a type intended for supercharging may be quite large; whereas,the volume of air contained within the cabin may be quite large, thevolume of air fed thereinto during a unit of time is comparativelysmall, so that an appreciable period of time is required to produce anoticeable change of pressure in the cabin. Similarly, the flow of airout through the outlet valve of the cabin is relatively small ascompared to the volume of the cabin, the result being that an excessflow of air through the outlet, as compared to the inlet flow of airthrough the air inlet, does not under ordinary valve control produce arapid change in the pressure within the cabin. The result of this isthat there may be a relatively rapid change in flight pressure without acorresponding change in cabin pressure, owing to the fact that thechange in cabin pressure lags.

The aircraft cabin comprises an air chamber of large volume having anair inlet duct I6 and an air outlet duct 94. The interior of the pipingI20, Fig. 1, comprises an air chamber of extremely small volume, thissmall air chamber being likewise fed with air through the inlet duct I6and exhausted through the outlet duct 94. The pressure in theintermediate portion of the small chamber formed by the piping I20 isdetermined by the relation existing between the flow of air fedthereinto from the inlet duct I6 and the flow of air taken from the rearend thereof through the outlet duct 94. Any change in these relativeinlet and outlet flows of air produces an immediate change in thepressure existing in the intermediate portion of the piping I20. Thisimmediate change in pressure .is transmitted through the valve 48 andthe pipe 30 to the interior of the case 26 of the control unit 24 .sothat there will be an immediate compensating action of the controldevice instead of a delayed operation of the control device 24,resulting when the pipe I30 thereof is connected to the cabin interior.

The control system also includes cascade vessels 92 in series with theinlet ducts I6 and the outlet ducts 94 substantially as shown in Fig. 1,the vessels serving to partially damp the amplitude of relatively shortand rapid pressure changes in the cabin caused by surges at the blowerinlet and cabin outlet.

A number of safety features must be observed in an aircraft cabinpressure re ulation system to insure passenger comfort and operationsafety. For example, safety valves I06 are provided in the large exhaustoutlets I8 and are set to relieve if the pressure differential exceedsthe design limit. A valve of this type may also be arranged to cut outthe fresh air flow increase control and/or the outlet valve closingcircuit. Non-return valves I08 are provided in the supercharger deliveryducts to prevent reverse flow in event of a compressor failure. A checkvalve I5 is arranged to open and thus prevent any appreciable suction inthe cabin when the airplane descends to altitudes below the pressureequalization altitude. This valve is preferably located in the ram ductwherein upon starting to supercharge it will close as soon as the cabinpressure exceeds the ram pressure.

While I have described my invention in its present embodiments, it willbe obvious to those skilled in the art, after understanding myinvention, that various changes may be made therein without departingfrom the scope thereof. I aim in the appended claims to cover all suchmodifications or changes.

I claim as my invention:

1. In an aircraft, a cabin adapted to be supercharged, a blower forsupplying air to said cabin at a pressure higher than that of theambient flight atmosphere, a compressed air inlet duct 5 from saidblower to said cabin, a vitiated air outlet duct from said cabin to theambient flight atmosphere, a controllable valve in said outlet duct, acabin pressure regulating device sensitive to cabin pressure and flightpressure, adjustable means on said device for setting said device torespond to an altitude at which cabin pressure is equalized with flightpressure, a conduit for taking pressure from said inlet duct near saidblower and transmitting said pressure to said regulating device, aconduit for taking pressure from said outlet duct near said outlet valveand transmitting said pressure to said regulating device, whereby thepressure differential between the inlet duct at the conduit connectionand the outlet duct at the conduit connection serves to anticipate cabinpressure changes before such changes are apparent in the said cabin, aprimary servo system responsive to said regulating device for openingand closing said outlet valve, and a secondary servo system responsiveto positions of said outlet valve for controlling the flow of compressedair from said blower to said cabin.

2. In an aircraft, a cabin adapted to be supercharged above the ambientatmospheric pressure, supercharging means comprising at least oneblower, an inlet duct from said blower to said cabin, at least oneoutlet valve for discharging vitiated air from said cabin, an outletduct leading from said cabin to said outlet valve, a servo systemarranged to control the aperture of said outlet valve, a regulatoradapted to normally control said servo system in response to departureof cabin pressure from a value functionally corre lated to flightaltitude pressure, and an anticipator system responsive to transient airpressure variations in the said inlet and outlet ducts and adapted toaccelerate the otherwise normal functioning of the said regulator, thesystem comprising a conduit connecting the regulator with a regionwithin the said inlet duct adjacent the blower wherein the air flowpressure is higher than cabin pressure, and a conduit connecting theregulator with a region within the said outlet duct adjacent the outletvalve wherein the air flow pressure is lower than cabin pressure,whereby the regulator will respond to transient flow quantity changeswithin the conduits prior to any appreciable change in cabin pressure asa direct result of said transient pressure variations. v

3. In regulating mean for an aircraft pressure cabin, the combination ofsupercharging means including an inlet duct through which air isdelivered into said cabin; an outlet duct leading from said cabin; aflow regulating valve associated with at least one of said ducts; aservo system arranged to control the aperture of said valve; a regulatoradapted to normally control said servo system in response to changesfrom predetermined relation of cabin pressure to external atmosphericpressure; and an anticipator system connected with said regulator andwith at least one of said ducts to transmit to said regulator theeffects of transient changes in air flow within at least one of saidducts before any appreciable change in pressure of the air Within thecabin can occur as. a'result of said transient changes.

4.. In pressure regulating means for an aircraft pressure cabin, thecombination of airflow means for delivering into and taking from thepressure cabin flow of air in such manner that the pressure in saidcabin will be controlled, saidairflow.

means including an inlet, means for charging air into the cabin throughsaid inlet, and an outlet path of flow for discharging air from thecabin, and a valve for controlling the discharge of air through saidoutlet so as to control the pressure in the cabin; and pressure actuatedregulating means operating to control said airflow means during flightso a to maintain in said cabin a pressure greater than the externalatmospheric pressure, said regulating means having a Pitot tube exposedto the flow of air in said inlet and a venturi in said outlet, and saidregulating means having responsive control means subjected to pressurechange in said Pitot tube and said venturi resulting from changes in therates of flow of air in said inlet and outlet.

5. In pressure regulating means for a pressure cabin, the combinationof: airflow means for delivering into and taking from the pressure cabinflows of air in such manner that the pressure in said cabin will becontrolled, aid airflow means including an inlet, means for charging airinto the cabin through said inlet, an outlet, means for discharging airfrom the cabin, and a valve for controlling the discharge of air throughsaid outlet so as to control the pressure in the cabin; and regulatingmeans operating to control said valve during flight so as to maintain insaid cabin a pressure greater than the external atmospheric pressure,said regulating means including pressure responsive control means, andfluid conduit means for transmitting to said pressure responsive controlmeans varying pressures resulting from changes in the flow in saidoutlet means and normally equal to cabin pressure, said conduit meansbeing adapted to, in response to transient flow changes in said outletmeans, transmit to said pressure responsive control means, pressurechanges effective thereon before corresponding transient changes in thepressure of the air within the cabin can occur.

6. In an aircraft, a cabin adapted to be supercharged, at least oneblower for supplying air to said cabin at a pressure higher than that ofthe ambient'flight atmosphere, a compressed air inlet duct from saidblower to saidcabin, a vitiated air outlet duct from said cabin to theambient flight atmosphere, a controllable valve in said outlet duct, apair of cascade vessels, one being in the inlet duct andone in theoutlet duct, said cascade vessels serving'to partially damp theamplitude of relatively short and rapid pressure changes in thecabincaused by surges of pressure at the blower inlet and cabin outlet, aregulating device including a chamber in which a simulated cabinpressure is maintained and mean in said chamber sensitive to thepressure in said chamber and to flight pressure, adjustable means forsetting said regulator to an altitude at which cabin pressure isequalized with flight pressure,

a primary servo system responsive to said regulator for opening andclosing said outlet valve, a secondary servo system responsive topositions of said outlet valve for controlling the flow of compressedair from said blower to said cabin,

, whereby the pressure in said cabin is controlled substantially ataratio of flight altitude pressure to the pressure insaidchamber, asgauged from the set equalizing altitude pressure; and means associatedwith the said regulating device for varying the ratio.

7. In pressure regulating means for a pressurized aircraft cabin, thecombination of: airflow means for circulating a flow of air underpressure through the cabin and including pressurizing inletmeans, outletmeans, valve means for controlling said flow, and pressure sensitiveregulator means for controlling said valve means and thereby controllingthe pressure in the cabin; and anticipating control means including aPitot tube and a venturi disposed in said inlet and outlet meanrespectively and sensitive to transient changes in difierential betweenquantities of flow in said inlet and outlet means respectively, adaptedto produce in said regulator means a response to said transient changesbefore any substantial change in the pressure of the cabinatmosphere canoccur as a result of said transientchanges.

8. In pressure regulating means for a pressurized aircraft cabin, thecombination of: airflow means for circulating a flow of air underpressure through the cabin and including inlet and outlet means, valvemeans for controlling the release of air through said outlet means, andpressure sensitive regulator means for controlling said valve means andthereby controlling the pressure in the cabin; anticipating controlmeans sensitive to transient changes in differential between quantitiesof flow in said inlet and outlet means respectively, adapted to producein said regulator means a response to said transient changes before anysubstantial change in the pressure of the cabin atmosphere can occur asa result of said transient changes; means for delivering air underpressure into said inlet means; means for quantitatively varying theoperation of said delivering means; and means controlled by said outletcontrol valve means for controlling the operation of said last means.

9. In pressure regulating means for a pressurized aircraft cabin, thecombination of: air.- flow means for circulating a flow of air underpressure through the cabin and including inlet and outlet means, valve:means for controlling said flow, and pressure sensitive regulator meansfor controlling said valve means and thereby controlling the pressure inthe cabin; anticipating control means ensitive to transient changes indifferential between quantities of flow in said inlet and outlet meansrespectively, adapted to produce in said regulator means a .response tosaid transient changes before any substantial change in the pressure ofthe cabin atmosphere can occur as a result of said transient changes;and means .to at least partially damp the amplitude of .relatively shortand rapid changes caused by surges in said inlet and outlet means.

10. In pressure regulating means for a pressurized aircraft cabin, thecombination of: airflow means for circulating a flow of air underpressure through the cabin and including pressurizing inlet means,outlet means, and valve means for controlling said flow; regulatingmeans including anticipating control means sensitive to transientchanges in differential between quantities of flow in said inlet andoutlet means respectively, adapted to adjust said valve means tocompensate for said transient changes before any substantial change inthe pressure of the cabin atmosphere can occur as a result of saidtransient changes; and means to at least partially damp the amplitude ofrelatively short and rapid pressure changes caused by surges in saidinlet and outlet means,

11. In pressure regulating'means for a pressurized aircraft cabin, thecombination of: airflow means for circulating a flow of air underpressure through the cabin and including pressurizing inlet means,outlet means, valve means for controlling the escape .of air throughsaid out let means and thereby controlling the pressure in the cabin;regulating means including .anticipating control means sensitive totransient changes in differential between quantities of flow in saidinlet and outlet means respectively, adapted to adjust said valve meansto compensate for said transient changes before any substantial 1 changein the pressure of the cabin atmosphere can occur as a result of saidtransient changes; and means controlled by said valve means in at leastone position thereof for quantitatively varying the input of saidpressurizing inlet means.

12. In pressure regulating means for a pressurized aircraft cabin, thecombination of: airflow means for circulating a flow of air underpressure through the cabin and including an inlet, a supercharger fordelivering air under pressure to said inlet, outlet means including avalve for permitting the controlled escape of air from the cabin andthereby controlling the pressure in the cabin; regulating meansincluding anticipating control means sensitive to transient changes indifferential between quantities of flow in said inlet and outlet meansrespectively, adapted to modify the position of said valve to compensatefor said transient changes before any substantial change in the pressureof the cabin atmosphere can result therefrom; inlet valve means forquantitatively varying the input from said supercharger; servo motormeans for operating said inlet valve means; and auxiliary control meansincluding an electric switch operated by said d'utlet valve means, forcontrolling the operation of said servo motor in response to changes incondition in said outlet means.

13. In pressure regulating means for an aircraft pressure cabin, thecombination of airflow means for delivering into and taking from thepressure cabin flows of air in such manner that the p168- sure in saidcabin will be controlled, said .airflow means definingan inlet path of.flow for charging the air and an outlet path of flow for dischargingair; regulating means automatically operable to control said airflowmeans durin flight so as to maintain in said cabin a pressure greaterthan the external atmospheric pressure; and pressure actuatedanticipating control means connected to said regulating means and havinga Pitot tube exposed to the flow of air in said inlet path and a venturiin said outlet path, said regulating means having responsive controlmeans subjected to the varying effects of the pressure changes in saidPitot tube and said venturi resulting from changes in the rates of flowof air in said inlet and outlet paths.

14. Means for regulating the pressure of the air within an aircraftcabin, comprising: airflow means for circulating air under pressure inthe cabin and including inlet and outlet means and a valve forcontrolling such circulation and thereby controlling the pressure of theair in the cabin; regulating means for controlling the aperture of saidvalve, including a pair of pressure responsive elements and servomechanism for transmitting the response of said elements to said valve;and cabin pressure change anticipating means including a pitot in saidinlet means, a venturi in said outlet means, and conduit means leadingfrom said pitot and venturi for directly subjecting said responsiveelements to variations in pressure resulting directly from changes inthe flows in said inlet .and outlet means, one of said pressureresponsive elements being sensitive to both ambient atmospheric pressureand the pressure imposed thereon by said conduit means and the other ofsaid pressure responsive elements being sensitive only to the pressure.imposed thereon by said conduit means, said cabin pressure changeanticipating means being adapted normally to cause the pressure to whichsaid responsive elements are subjected to substantially equal cabinpressure and being adapted, in response to transient changes in theflows in said inlet and outlet means, to effect stabilizing adjustmentof the aperture of said valve before corresponding transient changes inthe pressure of the air within said cabin can occur, said cabin pressurechange anticipating means including a pitot in said inlet means and aventuri in said outlet means.

BRUCE E. DEL MAR.

